1. Field of the Invention
The present invention relates to an electron beam lithography technique of character projection scheme for writing a circuit pattern of a semiconductor device by repeatedly exposing a small shaped beam. More particularly, the invention relates to a method of producing electron beam writing data and a program of producing electron beam writing data, which have a step of writing figure cells contained in device pattern data as a character pattern. Further, the invention relates to an electron beam writing apparatus comprising a function for producing electron beam writing data described above.
2. Description of the Related Art
In manufacturing a semiconductor device, electron beam (EB) lithography is used for exposure of a fine pattern which cannot be exposed in photo lithography. Among them, an EB direct writing technique is noticeable as a method for exposing a fine pattern with QTAT and low cost without a need for providing a mask for each pattern to be exposed. Further, a character projection (CP) scheme using an opening of a pattern to be repeatedly shot can reduce the number of EB shots and can improve a writing throughput as compared with a conventional variable shaped beam (VSB). Thus, there has been searched and developed an apparatus capable of using writing in the CP method as well as the VSB method.
In the EB direct writing using the CP method, one of the most important factors includes writing a character pattern. This writing denotes extracting a repetition pattern (character pattern) from pattern data to be written and assigning the extracted pattern to a character shot.
As a method for extracting a character pattern, there is used a method for producing data obtained by removing overlap from pattern data to be written and extracting a pattern formed in the same shape which is equal to or smaller than a maximum beam size (in general, several microns in square) (refer to Japanese Patent No. 2747573, for example). Further, there is used a method for using the figure cells of pattern data for carrying out writing as a character pattern (refer to Jpn. Pat. Appln. KOKAI Publication No. 2000-348084, for example).
Such a processing operation for extracting a character pattern, in general, is often carried in for data conversion for carrying out conversion in a writing data format specific to each EB writing apparatus from a general GDSII stream that is general as a format of layout data of the semiconductor device. However, in the case where the figure cells are used as a character pattern, it is necessary to edit or correct figure data serving as a character pattern in order to prevent double exposure before carrying out a data conversion processing operation.
The editing and correction of figure data used here denotes a work of correcting a pattern so as not to overlap with other cells relevant to the pattern data contained in the figure cells serving as a character pattern, or alternatively, extracting only a portion which is not overlapped, thereby using a character pattern. It is necessary for a user to carry out such a work manually by using a figure data editor such as a CAD, requiring a large amount of inconvenience.
As described above, conventionally, in the case where the figure cells contained in the cell-based device pattern is extracted as a character pattern, it has been necessary to edit or correct the figure data serving as a character pattern in order to prevent double exposure prior to carrying out a data conversion processing operation, and this editing and correction has been very cumbersome.